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Computer Networks
Pithirat Horvichien, Natalie Lowe, Adit Mohan, Bruno Hasenfratz,
Dev Mistry, Guy Levy
A Computer Network is a group of devices, which are
connected by communication links that are built using
physical media. Devices can be computers, telephones or
anything able to send or receive message. [1]
The Internet is a network of computer networks, which allows
transfer of information in an electronic format across the
globe in a very short time period. On the other hand Intranet
is the application of Internet technologies on a smaller scale
e.g. university, college, hospital etc. [2]
Client-Server Architecture is a form of technology that
separates computers and software into two groups: servers
and clients. The client provides the interface and application
processing, and the server provides the storage capacity, data
processing and graphics. For example, every computer
connected to a website acts as a client, while the websites
computer acts as a server. [3]
A Peer-to-Peer system uses the FTP (File Transfer Protocol)
whereby the client of one side contacts the server of the
other side and a file is transmitted accordingly. This differs
from client-server architecture as peers are equally privileged
in their application.
PAN (Personal Area Network) is a network covering a very
small area, such as a single room. The best-known example of
this is Bluetooth and USB technology. PAN also includes WiFi
as it can be used over a small area. LAN (Local Area Network),
covers small areas such as offices and homes. This connection
is mainly based on Ethernet, which can be supplied by
twisted-pair cables or wireless routers. WAN (Wide Area
Network) covers larger areas such as multiple buildings or a
college campus. The largest use of WAN is the Internet; this
can be used via fibre-optic cable or wirelessly via infrared
transmission or microwave technology. MAN (Metropolitan
Area Network) connects devices in the same metro area. For
example, a company located in Brno may have offices in
Prague and Plzen; all of their devices may be connected using
MAN. This is mainly done using microwave transmission
technology. [4]
IP stands for Internet Protocol address and is a numeric name
assigned to each device participating in the computer/internet
network.
Two versions of the Internet protocol are in use: IP-version 4
(IPv4) and IP-version 6 (IPv6) and each version is different
from the other in the way they define the address.
The original system called IPv4 (still used nowadays)
constitutes 32-bits number, and was lunched in 1983.
The newer version of the IP is version 6, which constitution
out of 128 bit number.
The IPv6 was developed by the Internet Engineering Task
Force (Organization for internet repair and maintain the
internet; it’s a volunteer organization) to deal with the longanticipated problem of IPv4 address exhaustion. [5]
IPv6 compared to IPv4:
•
Larger address space
•
Multicasting
•
Stateless address autoconfiguration (SLAAC)
•
Network-layer security
•
Simplified processing by routers
•
Mobility
•
Options extensibility
•
Jungbograms
•
Privacy
In general, a domain name (address) represents an Internet
Protocol resource, such as a personal computer used to access
the Internet, a server computer hosting a web site, or the web
site itself or any other service communicated via the Internet.
In 2015, 294 million domain names had been registered.
Domain names are used to establish a unique identity.
Organizations can choose the domain name that corresponds
to their name, hoping the Internet users to reach them more
quickly and easily.
An often-used analogy to explain the domain name system
(DNS) is that it serves as the „phone book“ of the Internet by
translating computer hostnames into to IP addresses. For
example, the domain name www.cookie.com translates to the
address
93.
183.
255.
117
(IPv4)
and
2700:2800:220:7b:25bf:1453:1994:aa7 (IPv6). In difference
from a phone book DNS can be rapidly updated, allowing the
IPs location on the network to change without effecting any
online users, whom continually using hostnames.
A Media Access Control address (MAC address) of each
computer is a unique identifier assigned to network interface
for communications, usually used in WIFI, local area network
(LAN). MAC addresses are often assigned by manufacturer of
the computer and is a specific identity of the computer. The
MAC address can been seen by the internet host (ISP: Internet
service provider). [6]
Common Internet Attack methods include Eavesdropping
(secretely listening to a private conversation without consent,
usually between hosts on a network (e.g. the FBI have been
accused of using programs to eavesdrop on suspicious
people)). Phishing (an attempt to obtain sensitive information
(e.g usernames and passwords, credit card details) by
masquerading as a trustworthy entity in an electronic
communication). DoS (Denial of service attack; overloading a
network by flooding it with useless traffic. Two types, this
normal type and DDoS (Distributed DoS) where several
computers flood a system with packets in a co-ordinated
fashion). Viruses (a piece of code which can copy itself and
typically has a detrimental effect such as destroying data.
Must attach itself to an existing program). Worms (Standalone
malware program that replicates itself and spreads to other
computers, often using a network to spread itself). Trojans (A
program, usually a virus hidden inside a harmless-looking file
or program. It isn’t activated until the file is opened, where it
then causes damage). Email Bombing (sending huge volumes
of emails to an address in an attempt to overflow the mailbox
or overwhelm the server). Spamming (use of electronic
messaging systems to send messages or advertising
repeatedly on the same site or to an email). Cookies (small
files stored on a user’s computer. Designed to hold a small
amount of data specific to a particular client or website).
Systems boot record infectors (virus that inserts its starting
code into the boot sector of a computer. When the computer
tries to boot up, the virus goes into the computer memory
and can gain control over basic operations).
Computer Security
Attributes
Confidentiality
Integrity
Privacy
Availability
Attack Methods
Eavesdropping, Hacking,
Phishing, DoS and IP
Spoofing
Viruses, Worms, Trojans,
Eavesdropping DoS and IP
Spoofing
Email Bombing, Spamming,
Hacking, DoS and Cookies
DoS, Email Bombing,
Spamming and Systems
Boot Record Infectors
Technology for Internet
Security
IDS, Firewall,
Cryptographic Systems,
IPSec and SSL
IDS, Firewall, Anti-Malware
Software, IPSec and SSL
IDS, Firewall, Anti-Malware
Software, IPSec and SSL
IDS, Anti-Malware Software
and Firewall
There are many gateways to protect computers against
network breaches; these include IDS, Firewall, Cryptographic
Systems and Anti-Malware. IDS (Intrusion Detection Systems)
is an extra protection measure designed to ward off computer
intrusions. Firewall is the front line of defence. Cryptographic
Systems involves the use of codes and ciphers to transform
data into nonsense data while transferring it in order to keep
it secure, this type of protection continues to advance as
hackers catch up with it. Anti-Malware is used to detect
Malware such as Trojans, worms and viruses and cure them if
they’re present. The difference between firewalls and Antimalware scanners is that firewalls control the information
sent to and from the device and blocks sites that may install
malware from accessing the device. Whereas Anti-Malware
programs look for and remove any malware present on the
device already. [7]
References;
[1] Ivan Marsic. (2010) Computer Networks: Performance &
Quality of Service.
[2] Vithal, GV, and Waghmode, SS., Intranet and Internet
[3]
http://www.businessdictionary.com/definition/clientserver-architecture.html
[4] David Delony. (2013) LAN WAN PAN MAN: Learn the
Differences Between These Network Types. Techopedia.com.
[5] http://www.whatismyipaddress.com/mac-address
[6] macvendors.com/what-is-mac_address
[7] Daya, B., Network Security: History, Importance, and
Future. University of Florida Department of Electrical and
Computer Engineering.